I've used a LensPen SensorKlean which has worked perfectly. Every method has it's pros and cons and you'll likely get multiple recommendations for how to do it. Some don't like wet cleaning because of possible residue and streaking. Some don't like dry cleaning because of possible scratching.

Received my copperhillimages.com cleaning kit for m43 and the illuminated
magnifier.
Using the 14mm sensorswipe wrapped with the PecPad and with 2 drops of the cleaning fluid was able to clean both my G1 and GF1.